Bevel gear-wheel



. E. H. WINGQVIST.

Patented Feb.V 24,

3 SHEETS-SHEET 3.

UNITED sir-Aras PATENT onirica. p

l ERIK HJALMAR WINGQVIST, F GOTTENBORG, SWEDEN, ASSIG-NOR T0AKTIEBOLAGET SVENSKA KULLAGERFABRIKEN, 0F GOTTENBORG, SIVEDEN, ACORPORATION OF SWEDEN.

BEVEL GEAR-WHEEL.

Specification of Letters Patent. Patented Feb. 24;, 1920.

Application filed July 17, 1917,'Seria1 No.,181,129. Renewed iApril 2,1919. Serial N0. 287,074.

To all whom t may concern.'

Be it known that I, ERIK HJALMAR WING Qvls'r, a subject of thev King ofSweden, residingl at Gottenborg, in the lKingdom of Sweden, haveinvented certain new and useful Improvements in Bevel Gear-Wheels,

l of which the following is a specification.

. surfaces and the pitch cone, if developed) ated,

in a plane, form involutes of a circle having its center at the apex ofthe pitch cone.

The ordinary bevel wheels of this kind are those having so-called spiralteeth, in which the lines of intersection between the side surfaces ofthe teeth and the pitch cone form curves which, if extended, ass throughthe apex of the pitch cone. Such a beve] wheel may be considered asgenerated by rolling a cone on a plane generating wheel in `which thelines of intersection between the generating teeth and theJ pitch coneform circular arcs passing, if extended, through the center of the pitchplane. Itis obvious that, in a gear wheel generated in such manner, theside surfaces of the teeth and also the lines coniining the bottomsurfaces of the tooth spaces converge toward the apex ofthe pitch coneof the wheel. As a consequence, the cross-section of the toothincreases, as in ordinary bevel wheels having radial teeth, inproportion to the square of the distance of the section from the apex ofthe pitch cone. In such case each gap must .be formed in two separateworking operations by two different tools. The said gear wheels offer,however, among other things the advantage that they can be genere for acertain pitch (or module), by a common generating wheel, z'. e., allgear wheels generated by rolling on one and the same generating wheelhave such a form of tooth and space as to be able to cooperate with eachother.

In order to simplify the manufacture of such gear wheels, it has beenproposed to make either the gapsy or the teeth of the same widththroughout, while maintaining the circular form of the above-namedsection of the teeth of the generating wheel.

I' the former case, each gap or tooth sp ce is cut in a single workingoperation b one and the same tool which is caused to si ing abouta fixedpoint. It is obvious, however, that the relative enlargement of thespace toward the apex of the pitch cone entails a correspondingweakening of the cross-section of the tooth in the same direc tion.Moreover, the serious objection arises that two gear wheels manufacturedin such manner cannot coperate with each other, inasmuch as a toothhaving a decreasing cross-section cannot work in a space of uniformwidth.

In the latter case, the whole tooth proiile is cut by a tool which islikewise adapted to swing about a fixed point. It is true that in suchmanner a tooth of uniform width will be obtained, but, inasmuch as inIthis case the width of the space will decrease correspondingly towardthe apex of the pitch cone of the wheel, it is also easily seen that twogear wheels manufactured in such manner cannot coperate with each other.

On the other hand, a gear wheel manufactured in the first-mentionedmanner can, under certain conditions, cooperate with a gear wheelmanufactured in the last-men- .tioned manner. This necessitates,however,

that in making a pair of gear wheels, or a gear, two separate methods ofmanufacturing and two different tools must be employed, and, moreover,the serious'objection arises that the power of resistance of the gearwill be limited to the power of resist- Aance of the wheel of the pairhaving, as hereinbefore set forth, the considerably weakened teeth. Sofar as strength is-concerned, nothing is gained in thus making the teethof one wheel of the pair of uniform width, the net result being aIweakening of the `According to my present invention, all the aforesaiddlsadvantages, either of the normal spiral -gear wheels or of theabnormal ones, are avoided by a constructionwherein the lines ofintersection between the side `sur` faces of the teeth and the pitchcone, when z'. e., by the same tool and in the same man# apex of thepitch cone. By this formation, the lteeth and the spaces will be ofuniform width throughout, (measured inthe pitch cone) i. e., at thesaine time as a tooth of .uniform Width throu vhlout is obtained, aWhole' tooth space can be formed in a single working operation by aysingle tool. Morcover, by one and the same generating wheel,

ner, different series of gear wheels of the came module can begenerated, all ofwhich are capable of coperation with one another.

In the accompanying drawings some conv structions of theV invention areshown.

Figure 1 is a section of a generating wheel and a bevel gear wheelaccording to the invention during the generating process;v

' Fig. 2 is a plan of the wheels of- Fig. l,

the' generating wheel and the Wheel generated being, for the sake ofsimplicity, represented on sections through their pitch cones,

f the plane of section being indicated by thel line A-B of Fig. 2;

yat

respectively A Fig. 3 isa section of the generating Wheel,

Fig. 9 is a plan View of the wheel shown in Fig. 8, the plane ofsection, of Fig. 8 heing indicated in this view by the line E-F.

In Figs. l and 2, 1 designates the plane generating wheel and 2 thebevel wheel generated by rolling'tliereon. In this illustration, theteeth of the generating` wheel are v shown of uniform height throughoutand of straight profile, z'. e., they each have, in crosssectlon, theforni of a truncated wedge having straight sides, as clearly showninFig. 3.

.In Fig. 2 3 designates the linesof interseca tion between the pitchplane of the generating-wheel and the generating teeth. In

' the form of embodiment shown, said lines of intersection are formed asinvolutes of the circle 4, the plane of the section of Fig. 3` being onthe line A-B and tangential to such circle. The perpendicular distancebetween ltwo successive involutes beingknown to be always constant andequal to the pitch at the base circle 4, it follows that both the toothand thegap or tooth space will be of .iniform width wherever they be cutby planes at right angles to the involutes. The

teeth ofthe generating wheel are of uni- ,'86 form height and width,vand the spaces are .responding to the teethA also of Iuniform width. Itis, however, to

be observed that, if a tooth be cut by a series of cylinders placedconcentrically around the axis of the generating Wheel, the crosssectionincreases, as usual, as the distance of the section from the center ofthe pitch plane increases. Obviously, this isalso the case as regardsthe gap.

From the foregoing lit is apparent that, if a bevel gear Wheel'begenerated by yrolling upon such a generating wheel, as is 'abovedescribed, the teeth and spaces of such generated wheel will also be ofuniform Width.

'This is illustrated in Fig. 2, where the in- From this it follows thatthe teeth and the.' 90

spaces must be of uniform width also in the generated wheel 2. In otherwords, the teeth of the Wheel 2 will obtain a form corof the generatingwheel, z'. e., they will be of uniform width and uniformheighn,whereasthe tooth profile Will not be straight, but curved. If, on the otherhand, a tooth be cut by parallel planes at right angles to a generatingline of the pitchv cone, the cross-section of the tooth will increase,just as in the generating wheel, according as the distance of thesection from the apex of thepitch cone increases. y s n The carryinginto practice of this rolling generation can be performed by a cuttingtool having a. profile corresponding to the tooth 'profile of thegenerating Wheel, z'. e., having in profile the form of a truncatedwedge with straight sides, -said tool, while being caused to perform acutting movement Ain thedirection of an involute of the generatingwheel, being caused to simultaneously describe such a rolling movementrelatively to the gear wheel blank as would be described by a tooth ofthe generating wheel meshing with the gear Wheel to be generated.

A bevel wheel generated in that manner is shown in Figs. 4 and 5. Itappears that each tooth is of uniform height from end to end, and thebottoni and top surfaces are parallel to the pitch cone. In order toobtain the desired uniform width of the tooth and space, it is evidentlynecessary to cause the wedge-shaped cutting' tool to cut into the wheelblank to the same extent at both ends of the space, by which the toothobtains the uniform height shown. Furthermore, on account of the toothbeing of uniform Width, as stated, the result Will be a tooth of uniformstrength along its Whole length. The tooth profile will be curved and ofthe form shown in Fig. 6.

A gear Wheel of the kind described can also be manufactured by hotrolling in such manner that the red hot gear Wheel blank is caused toroll, under pressure, against the generating Wheel.

Obviously, the teeth of the one Wheel of apair of Wheels can be madewith a straight profile, as shown in F ig. 7. This entails thesimplification of manufacture, as regards one Wheel of the pair, thatthe Wedge-shaped tool has only to perform the cutting move menthereinbefore set forth, but no rolling movement relatively to the Wheelblank. On the other hand, the second Wheel of the air must be generatedby rolling on the irstmentioned Wheel, z'. c., either by hot rolling orby means of a Wedge-shaped cutting tool having the same profile as theteeth of the latter Wheel,l said tool having to perform in such caseboth a cutting and a rolling movement. operation of the teeth Will betheoretically correct, whethen-both'wheels be generated byY a commongenerating Wheel, in which case they will both obtain a curved toothprofile, or one Wheel be made with straight tooth prole and employed ingenerating the second wheel of the pair;

Figs. 8 and 9 show a so-called V-teothed bevel gear Wheel having teethaccording to the invention. In this case, the teeth of the tivo sectionsof the Wheel form an angle with each other, in a known manner. In orderto be able to cut the inner parts of the spaces, the Wheel blank 6' hasvan annular .slot 7 in which the cutting tools working fromopposite endshave sufficient play to move` Without interfering with the oppositesection. Obviously, also this gear Wheel can he made with a straighttooth profile or with a curved one. Instead of making use of the slot 7,peripherally arranged holes may be provided, the number of whichcorresponds to that of thc tooth spaces; by this means the teeth of thetWo wheel 'sections are unin- It is, however, obvious,- that thecoterrupted at their inner ends andare con scquently stronger.

The 'described method of making the gear wheels herein set forth is notclaimed in this application, beinof made the subjectof an applicationfiled iilarch 14, l1918, Serial No. 222,385.

It is to be understood that the gear Wheels herein shown areillustrative of my invention and that changes may be made Within thescope of the claims, Without departing from the spirit of the invention.

What I claim is l. A bevel gear Wheel having the teeth and tooth spaces(measured in the pitch conc) each of uniform width in all sections atright angles to the side surfaceof the ll'ooth.

2. A bevel gear wheel having the side surfaces of its teeth so formedthat the lines of intersection between such side surfaces and the pitchcone, when developed in a plane, form involutes of a circle having itscenter at the apex of the pitch cone.

A bevel gear wheel according to claim l', having the teeth of uniformheight, the Icross-section of each tooth being constant throughout itslength.

4. A bevel gear Wheel according to claim l, having 'the teeth of theform which would be obtained by the rolling of a cone on a generatingwheel, the teeth of which form,

in cross-section, a truncated Wedge havingv straight sides, and in whichthe lines 0f intcrscction between the generating teeth and the pitchcone, if developed in a plane, form iuvolutes of a circle having itscenter at the apex of the pitch cone.

5. A bevel gear wheel according to claim l, having the teeth of theforni which would be obtained by the rolling of a conel on a generatingwheel, having teeth the lines of which intersecting the pitch plane,form involutcs of a circle the center of which coincides with the centerof said Wheel and the apex ofv the pitch cone of such bevel gear.

In witness whereof I have hereunto signed my name.

ERIK AHJALMAR WINGQVIST.

